1. Field of the Invention
The present invention relates to a method for producing a liquid transport apparatus and the liquid transport apparatus.
2. Description of the Related Art
The liquid transport apparatus for transporting the liquid includes an ink-jet head for jetting an ink from nozzles to perform the printing.
For example, an ink-jet head, which is shown in FIGS. 16 and 17 of Japanese Patent Application Laid-open No. 2006-96034, comprises a flow passage unit which is provided with a plurality of pressure chambers communicated with nozzles, a vibration plate which covers the plurality of pressure chambers formed in the flow passage unit, a piezoelectric layer which is arranged on the upper surface of the vibration plate, and a plurality of individual electrodes which are arranged respectively in areas opposed to the plurality of pressure chambers on the upper surface of the piezoelectric layer.
A method for producing the ink-jet head includes firstly joining the vibration plate to the flow passage unit, subsequently forming the piezoelectric layer on the vibration plate, for example, by means of the CVD method or the AD method, and finally forming the individual electrodes at the predetermined positions corresponding to the respective pressure chambers on the piezoelectric layer.
When a predetermined driving voltage is applied between the individual electrode which is positioned on the upper surface of the piezoelectric layer and the vibration plate which serves as the common electrode positioned under or below the piezoelectric layer in the ink-jet head, then the piezoelectric layer is shrunk, and the bending deformation arises in the vibration plate. The volume of the pressure chamber is changed in response to the deformation of the vibration plate. Accordingly, the pressure is applied to the ink contained in the pressure chamber, and the ink is discharged from the nozzles.
On the other hand, Japanese Patent Application Laid-open No. 2006-96034 discloses an ink-jet head including individual electrodes which are formed in areas, on an upper surface of a piezoelectric layer, corresponding to circumferential edge portions of pressure chambers. This ink-jet head performs the so-called pull type jetting operation (pulling jet operation). The pull type jetting operation resides in the following driving method. That is, when the driving voltage is applied to the individual electrode, then the vibration plate is deformed so that the vibration plate is convex on the side opposite to the pressure chamber (to increase the volume of the pressure chamber), and the ink is introduced into the pressure chamber from the common liquid chamber. After that, the application of the driving voltage is stopped, and the deformation of the vibration plate is returned to provide the original form. Accordingly, the discharge pressure is applied to the ink contained in the pressure chamber.
A groove is formed in an area of the vibration plate opposed to a central portion of the pressure chamber in the ink-jet head. The area of the vibration plate formed with the groove has the rigidity which is lower than any other area formed with no groove, because the area formed with the groove is thin as compared with the area formed with no groove. As a result, the deformation of the vibration plate is caused with ease, and it is possible to lower the driving voltage.
The method for producing the ink-jet head described in Japanese Patent Application Laid-open No. 2006-96034 includes performing the positioning so that the groove is arranged while being overlapped with the central portion of the pressure chamber as viewed in the direction perpendicular to the vibration plate, joining the vibration plate and the flow passage unit to one another in this state, forming the piezoelectric layer over the entire region on the vibration plate after the joining, and forming the individual electrodes corresponding to the respective pressure chambers. In this procedure, the individual electrode is formed at the predetermined position on the basis of the groove positioned corresponding to the central portion of the pressure chamber.
However, when the vibration plate and the flow passage unit are pressed and joined to one another, the pressing force, which presses the vibration plate and the flow passage unit in the vertical direction, is also dispersed in the planar direction or the horizontal direction of the vibration plate and the flow passage unit in some cases. The vibration plate and the flow passage unit are sometimes joined to one another while being deviated by the dispersed force in the planar direction with respect to the arrangement in which the vibration plate and the flow passage unit are positioned.
As a result, the grooves are positioned while being deviated from the central portions of the pressure chambers. However, even in such a situation, the individual electrodes have been hitherto formed at the predetermined positions on the basis of the grooves as described above. Therefore, the individual electrodes are also formed at the deviated positions in some cases in the same manner as the grooves.
As a result, the area of the piezoelectric layer, which is deformed when the driving voltage is applied, is decreased. Any sufficient discharge pressure is not applied to the ink contained in the pressure chamber, and the ink is not discharged appropriately from the nozzles in some cases.